U.S. patent application number 16/360535 was filed with the patent office on 2019-09-26 for transistor and method for manufacturing the same.
The applicant listed for this patent is Innoscience (Zhuhai) Technology Co., Ltd.. Invention is credited to Junyoun Kim, Jin Wei.
Application Number | 20190296139 16/360535 |
Document ID | / |
Family ID | 63196629 |
Filed Date | 2019-09-26 |
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United States Patent
Application |
20190296139 |
Kind Code |
A1 |
Wei; Jin ; et al. |
September 26, 2019 |
Transistor and Method for Manufacturing the Same
Abstract
The present application provides a transistor and a
manufacturing method thereof, and can at least partially solve the
problem of degraded characteristics and deteriorated reliability
with use of existing transistors with a P-cap layer. The transistor
includes: a channel layer and a barrier layer stacked on top of
each other; and a source, a drain, and a gate spaced apart from one
another on a side of the barrier layer distal to the channel layer.
The gate is between the source and the drain, a P-cap layer is
provided between the barrier layer and the gate, and a Schottky
contact is formed between the P-cap layer and the gate. Two side
edge regions of the P-cap layer respectively close to the source
and the drain are two electric field modulation regions spaced
apart from each other and capable of inducing positive charges
under a positive gate-source voltage.
Inventors: |
Wei; Jin; (Zhuhai, CN)
; Kim; Junyoun; (Zhuhai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Innoscience (Zhuhai) Technology Co., Ltd. |
Zhuhai |
|
CN |
|
|
Family ID: |
63196629 |
Appl. No.: |
16/360535 |
Filed: |
March 21, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/7786 20130101;
H01L 29/2003 20130101; H01L 29/205 20130101; H01L 21/2654 20130101;
H01L 29/1066 20130101; H01L 29/207 20130101; H01L 29/0607 20130101;
H01L 29/66462 20130101 |
International
Class: |
H01L 29/778 20060101
H01L029/778; H01L 29/20 20060101 H01L029/20; H01L 29/205 20060101
H01L029/205; H01L 29/66 20060101 H01L029/66; H01L 21/265 20060101
H01L021/265 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2018 |
CN |
201810251454.4 |
Claims
1. A transistor, comprising: a channel layer and a barrier layer
stacked on top of each other; and a source, a drain, and a gate
spaced apart from one another on a side of the barrier layer distal
to the channel layer, wherein the gate is between the source and
the drain, a P-cap layer is provided between the barrier layer and
the gate, and a Schottky contact is formed between the P-cap layer
and the gate, wherein two side edge regions of the P-cap layer
respectively close to the source and the drain are two electric
field modulation regions spaced apart from each other, and the
electric field modulation regions are capable of inducing positive
charges under a positive gate-source voltage.
2. The transistor of claim 1, wherein the electric field modulation
regions are high resistance zones formed by doping two side edge
regions of the P-cap layer respectively close to the source and the
drain with a doping element.
3. The transistor of claim 3, wherein the doping element comprises
any one or more of argon, fluorine, nitrogen, oxygen, silicon,
iron, carbon, and boron.
4. The transistor of claim 1, wherein the P-cap layer has a
thickness of 20 nm to 1000 nm, and each of the electric field
modulation regions extends downward from a surface of the P-cap
layer close to the gate by an extending distance less than or equal
to the thickness of the P-cap layer.
5. The transistor of claim 1, wherein of the two electric field
modulation regions, one close to the source is a first electric
field modulation region, and the other close to the drain is a
second electric field modulation region, an edge of the first
electric field modulation region close to the source is an edge of
the P-cap layer close to the source, an edge of the first electric
field modulation region distal to the source is between a first
limit and a second limit, the first limit is 400 nm away from a
first edge line and at a side of the first edge line close to the
source, and the second limit is 500 nm away from the first edge
line and at a side of the first edge line distal to the source, the
first edge line being an edge line, close to the source, of a
contacting area between the gate and the P-cap layer, and an edge
of the second electric field modulation region close to the drain
is an edge of the P-cap layer close to the drain, an edge of the
second electric field modulation region distal to the drain is
between a third limit and a fourth limit, the third limit is 400 nm
away from a second edge line and at a side of the second edge line
close to the drain, and the fourth limit is 500 nm away from the
second edge line and at a side of the second edge line distal to
the drain, the second edge line being an edge line, close to the
drain, of the contacting area between the gate and the P-cap
layer.
6. The transistor of claim 1, wherein the transistor is a gallium
nitride transistor.
7. The transistor of claim 1, further comprising: a substrate,
wherein the channel layer is closer to the substrate than the
barrier layer.
8. A method for manufacturing a transistor, wherein the transistor
is the transistor of claim 1, and the method comprises: a step of
forming the channel layer and the barrier layer, a step of forming
the P-cap layer having the electric field modulation regions, and a
step of forming the source, the drain, and the gate.
9. The method of claim 8, wherein the step of forming the P-cap
layer having the electric field modulation regions comprises:
forming a P-type semiconductor material layer, doping two regions
of the P-type semiconductor material layer spaced apart from each
other to form high resistance zones by ion implantation, and then
etching the P-type semiconductor material layer such that the
remaining P-type semiconductor material layer forms the P-cap layer
and the remaining high resistance zones form the electric field
modulation regions.
10. The method of claim 8, wherein the step of forming the channel
layer and the barrier layer comprises: forming the channel layer
and the barrier layer by epitaxial growth, respectively.
11. The method of claim 8, wherein the step of forming the P-cap
layer having the electric field modulation regions comprises:
forming the P-cap layer, and doping the two side edge regions of
the P-cap layer respectively close to the source and drain to form
high resistance zones by ion implantation, the high resistance
zones being electric field modulation regions.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Chinese Patent
Application No. 201810251454.4 filed Mar. 26, 2018, the disclosure
of which is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure belongs to the technical field of
transistors (especially GaN transistors), and in particular relates
to a transistor and a manufacturing method thereof.
BACKGROUND
[0003] Gallium nitride (GaN) semiconductors have characteristics
such as large band gap, high breakdown voltage, high electron
saturation velocity, high drift velocity, etc. Therefore, a gallium
nitride transistor fabricated using a GaN semiconductor has
advantages such as high breakdown voltage, low on resistance, fast
response speed, and the like, and is thus especially suited to
serve as a switching element.
[0004] As shown in FIG. 1, in order to improve performance of a GaN
transistor, the GaN transistor is formed as an Enhancement-mode GaN
high electron mobility transistor (E-mode GaN HEMT), with a P-cap 3
being inserted between a gate 23 and a barrier layer 12 thereof.
However, for such GaN transistor, when a positive gate-source
voltage reaches a certain value, a PN junction between the P-cap
layer 3 and a channel is turned on, resulting in a large gate
current. To avoid this problem, a Schottky contact may be formed
between the gate 23 and the P-cap layer 3, i.e., a Schottky
junction is formed, and therefore, when a positive gate-source
voltage is applied, the Schottky junction may withstand a part of
the voltage, which increases an allowable range of a gate voltage
and avoids a large gate current.
[0005] However, when a positive gate-source voltage is applied, the
Schottky junction between the gate 23 and the P-cap layer 3 may be
subjected to a reverse bias voltage and generate an electric field
at the Schottky junction, and intensities of the electric field at
two edge areas (i.e., areas enclosed by dotted lines in the
drawing) of the Schottky junction respectively close to a source
and a drain are much greater than that at the center region. Thus,
the high electric field at the edges of the Schottky junction may
degrade characteristics of the device and deteriorate reliability
of the device during long term operation.
SUMMARY
[0006] The present disclosure at least partially solves the problem
that an existing transistor provided with a P-cap layer may have
degraded characteristics and deteriorated reliability with use, and
provides a transistor whose characteristics can be avoided from
being degraded and whose reliability is good.
[0007] In one aspect, the present disclosure provides a transistor,
including:
[0008] a channel layer and a barrier layer stacked on top of each
other;
[0009] a source, a drain, and a gate provided spaced apart from one
another on a side of the barrier layer distal to the channel layer,
wherein the gate is between the source and the drain, a P-cap layer
is provided between the barrier layer and the gate, and a Schottky
contact is formed between the P-cap layer and the gate; and
[0010] two side edge regions of the P-cap layer respectively close
to the source and the drain are two electric field modulation
regions spaced apart from each other, and the electric field
modulation regions are capable of inducing positive charges under a
positive gate-source voltage.
[0011] Optionally, the electric field modulation regions are high
resistance zones formed by doping the two side edge regions of the
P-cap layer respectively close to the source and the drain with a
doping element.
[0012] Further optionally, the doping element includes any one or
more of argon, fluorine, nitrogen, oxygen, silicon, iron, carbon,
and boron.
[0013] Optionally, the P-cap layer has a thickness of 20 nm to 1000
nm; and
[0014] each of the electric field modulation regions extends
downward from a surface of the P-cap layer close to the gate by an
extending distance less than or equal to the thickness of the P-cap
layer.
[0015] Optionally, of the two electric field modulation regions,
one close to the source is a first electric field modulation
region, and the other close to the drain is a second electric field
modulation region; an edge of the first electric field modulation
region close to the source is an edge of the P-cap layer close to
the source, an edge of the first electric field modulation region
distal to the source is between a first limit and a second limit,
the first limit is 400 nm away from a first edge line and at a side
of the first edge line close to the source, and the second limit is
500 nm away from the first edge line and at a side of the first
edge line distal to the source, the first edge line being an edge
line, close to the source, of a contacting area between the gate
and the P-cap layer; and
[0016] an edge of the second electric field modulation region close
to the drain is an edge of the P-cap layer close to the drain, an
edge of the second electric field modulation region distal to the
drain is between a third limit and a fourth limit, the third limit
is 400 nm away from a second edge line and at a side of the second
edge line close to the drain, and the fourth limit is 500 nm away
from the second edge line and at a side of the second edge line
distal to the drain, the second edge line being an edge line, close
to the drain, of the contacting area between the gate and the P-cap
layer.
[0017] Optionally, the transistor is a gallium nitride
transistor.
[0018] Optionally, the transistor further includes:
[0019] a substrate, wherein the channel layer is closer to the
substrate than the barrier layer.
[0020] In another aspect, the present disclosure provides a method
for manufacturing the above transistor, which includes:
[0021] a step of forming the channel layer and the barrier layer, a
step of forming the P-cap layer having the electric field
modulation regions, and a step of forming the source, the drain,
and the gate.
[0022] Optionally, the step of forming the P-cap layer having the
electric field modulation regions includes:
[0023] forming a P-type semiconductor material layer, doping two
regions of the P-type semiconductor material layer spaced apart
from each other to form high resistance zones by ion implantation,
and then etching the P-type semiconductor material layer such that
the remaining P-type semiconductor material layer forms the P-cap
layer and the remaining high resistance zones form the electric
field modulation regions;
[0024] or,
[0025] forming the P-cap layer, and doping the two side edge
regions of the P-cap layer respectively close to the source and the
drain to form high resistance zones by ion implantation, the high
resistance zones being electric field modulation regions.
[0026] Optionally, the step of forming the channel layer and the
barrier layer includes:
[0027] forming the channel layer and the barrier layer by epitaxial
growth, respectively.
[0028] In the transistor of the present disclosure, an electric
field modulation region is provided at an edge of the gate (that
is, at an edge of the Schottky junction), and the electric field
modulation regions can induce extra positive charges at a positive
gate-source voltage, so that electric lines of force meant to be
connected between the gate and edge areas of the P-cap layer may be
partially cut off in the electric field modulation regions, which
reduces the actual electric field intensity at the edge of the
Schottky junction, thereby avoiding characteristics of the device
from being degraded and improving reliability of the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic cross-sectional view of a structure of
a conventional transistor;
[0030] FIG. 2 is a schematic cross-sectional view of a structure of
a transistor according to an embodiment of the present
disclosure;
[0031] FIG. 3 is a partially enlarged cross-sectional view of a
P-cap layer of a transistor according to an embodiment of the
present disclosure;
[0032] FIG. 4 is a partially enlarged cross-sectional view of a
P-cap layer of another transistor according to an embodiment of the
present disclosure;
[0033] FIG. 5 is a schematic cross-sectional view of a structure
after forming a P-type semiconductor material layer in a method for
manufacturing a transistor according to an embodiment of the
present disclosure;
[0034] FIG. 6 is a schematic cross-sectional view of a structure
after forming a high resistance zone in a P-type semiconductor
material layer in a method for manufacturing a transistor according
to an embodiment of the present disclosure; and
[0035] FIG. 7 is a schematic cross-sectional view of a structure
after forming a P-cap layer in a method for manufacturing a
transistor according to an embodiment of the present
disclosure.
[0036] Reference Numerals: 11: channel layer; 12: barrier layer;
21: source; 22: drain; 23: gate; 3: P-cap layer; 39: P-type
semiconductor material layer; 5: electric field modulation region;
51: first electric field modulation region; 52: second electric
field modulation region; 59: high resistance zone; 7: transition
layer; 8: insulating layer; 9: substrate.
DETAILED DESCRIPTION
[0037] To enable those skilled in the art to better understand
technical solutions of the present disclosure, the present
disclosure will be described in detail below in conjunction with
the accompanying drawings and specific implementations.
[0038] As shown in FIGS. 2 to 7, the embodiment provides a
transistor, which includes: a channel layer 11 and a barrier layer
12 stacked on top of each other; a source 21, a drain 22 and a gate
23 spaced apart from one another at a side of the barrier layer 12
distal to the channel layer 11, wherein the gate 23 is between the
source 21 and the drain 22, a P-cap layer 3 is provided between the
gate 23 and the barrier layer 12, and a Schottky contact is formed
between the P-cap layer 3 and the gate 23.
[0039] As shown in FIG. 2, the transistor in the embodiment
includes the channel layer 11 and the barrier layer 12 stacked on
top of each other, a heterojunction is formed between the channel
layer 11 and the barrier layer 12, and the barrier layer 12 has
larger band gap than the channel layer 11, so that two-dimensional
electron gas (2DEG) may be formed at a side of the heterojunction
boundary close to the channel layer 11. The source 21, the drain
22, the gate 23 are provided at a side of the barrier layer 12
distal to the channel layer 11, the source 21 and the drain 22 are
in direct contact with the barrier layer 12, the gate 23 is located
between the source 21 and the drain 22, the P-cap layer 3 is
provided between the gate 23 and the barrier layer 12, and the
P-cap layer 3 is made of a P-type doped semiconductor material and
configured to deplete the 2DEG in a channel under the gate 23.
Moreover, a Schottky contact (or a Schottky junction) is formed
between the P-cap layer 3 and the gate 23, so that when a positive
gate-source voltage is applied, the Schottky junction can withstand
a part of the voltage, thereby increasing allowable range of a gate
voltage, and avoiding a large gate current.
[0040] Specifically, as shown in FIG. 2, an insulating layer 8 may
further be provided on the side of the barrier layer 12 distal to
the channel layer 11. The source 21, the drain 22, and the gate 23
may contact with the barrier layer 12 or the P-cap layer 3 through
via holes in the insulating layer 8.
[0041] In an embodiment, the transistor further includes a
substrate 9, and the channel layer 11 is closer to the substrate 9
than the barrier layer 12.
[0042] That is, the barrier layer 12 may be farther from the
substrate 9 than the channel layer 11, and then the source 21, the
drain 22, and the gate 23 are located on a side of the barrier
layer 12 distal to the substrate 9.
[0043] In an embodiment, the transistor further includes a
transition layer 7 provided between the substrate 9 and the channel
layer 11.
[0044] Since the barrier layer 12, the channel layer 11, and the
like are usually prepared by epitaxial growth, and lattice
parameters or the like of materials of these layers may not match
with that of a material of the substrate 9, a transition layer 7,
which adjusts stress in the crystal growth process, may be provided
between the substrate 9 and the channel layer 11, so that a
high-quality channel layer 11 can be grown on the transition layer
7.
[0045] In an embodiment, the transistor is a GaN transistor.
[0046] For example, in a GaN transistor, the substrate 9 may be
made of a material selected from any one of silicon (Si), sapphire,
aluminum nitride (AlN), gallium nitride (GaN), silicon carbide
(SiC), and the like; the transition layer 7 may be made of a
material including any one or more of gallium nitride (GaN),
aluminum nitride (AlN), and aluminum gallium nitride (AlGaN); the
channel layer 11 may be made of a material selected from any one of
gallium nitride (GaN), aluminum gallium nitride (AlGaN), indium
gallium nitride (InGaN), aluminum indium gallium nitride (AlInGaN)
and indium aluminum nitride (AlInN); the barrier layer 12 may be
made of a material including any one or more of gallium nitride
(GaN), aluminum gallium nitride (AlGaN), indium gallium nitride
(InGaN), aluminum indium gallium nitride (AlInGaN), and indium
aluminum nitride (AlInN), wherein at least one material in the
barrier layer 12 have a band gap greater than a band gap of the
material of the channel layer 11; and the P-cap layer 3 may be made
of a material including any one or more of P-type doped gallium
nitride (GaN), P-type doped aluminum gallium nitride (AlGaN),
P-type doped indium gallium nitride (InGaN), P-type doped aluminum
indium gallium nitride (AlInGaN), and P-type doped aluminum indium
nitride (AlInN).
[0047] Needless to say, the specific structure, material, and the
like of the transistor of this embodiment are not limited thereto.
For example, the insulating layer 8 may be absent at the side of
the barrier layer 12 distal to the channel layer 11, and the source
21, the drain 22, and the gate 23 may be in direct contact with the
barrier layer 12 or the P-cap layer 3. For another example, the
source 21 and the drain 22 may be in direct contact with the
channel layer 11. For another example, the barrier layer 12, the
channel layer 11, and other layer(s) of the transistor may also be
made of other known materials.
[0048] In the transistor of the embodiment, the two side edge
regions of the P-cap layer 3 respectively close to the source 21
and the drain 22 are two electric field modulation regions 5 spaced
apart from each other. The electric field modulation regions 5 are
able to induce positive charges at a positive gate-source
voltage.
[0049] As shown in FIG. 2, the two side edges of the P-cap layer 3
of the transistor of the embodiment close to the source 21 and the
drain 22 are both electric field modulation regions 5, and the
electric field modulation region 5 refers to a region able to
induce positive charges under the positive gate-source voltage.
[0050] In an existing transistor, when a positive gate-source
voltage is applied, a certain number of positive charges are
induced in the gate 23, and a certain number of negative charges
are induced in the P-cap layer 3, thereby forming an electric field
therebetween. Due to electric field edge-crowding effect, intensity
of the electric field at an edge of the Schottky junction (i.e.,
edges of the gate 23 respectively closer to the source 21 and the
drain 22) is greater, which is likely to render the device with
degraded characteristics and deteriorated reliability.
[0051] In the transistor of the embodiment, the electric field
modulation regions 5 are provided at the edges of the gate 23
(i.e., at the edge of the Schottky junction), and the electric
field modulation regions 5 can induce extra positive charges at a
positive gate-source voltage, so that electric lines of force meant
to be connected between the gate 23 and edge areas of the P-cap
layer 3 may be partially cut off in the electric field modulation
regions 5, which reduces the actual electric field intensity at the
edge of the Schottky junction, thereby avoiding characteristics of
the device from being degraded and improving reliability of the
device.
[0052] In an embodiment, each of the electric field modulation
regions 5 is a high resistance zone formed by doping the two side
edge regions of the P-cap layer 3 close to the source 21 and the
drain 22 with a doping element. In an embodiment, the doping
element includes any one or more of argon (Ar), fluorine (F),
nitrogen (N), oxygen (O), silicon (Si), iron (Fe), carbon (C), and
boron (B).
[0053] That is, the P-cap layer 3 may be doped with one or more of
the above-mentioned materials that are generally used for forming a
high resistance zone, and the doped high resistance zone is the
electric field modulation region 5.
[0054] In an embodiment, the P-cap layer 3 has a thickness in the
range of 20 nm to 1000 nm; the electric field modulation region 5
extends downward from a surface of the P-cap layer 3 close to the
gate 23, and an extending depth is less than or equal to the
thickness of the P-cap layer 3.
[0055] As shown in FIGS. 3 and 4, the thickness H of the entire
P-cap layer 3 preferably satisfies: 20 nm.ltoreq.H.ltoreq.1000 nm.
Moreover, the electric field modulation region 5 is at least
located at the surface of the P-cap layer 3 close to the gate 23,
and extends from the surface to the inside of the P-cap layer 3 by
a certain depth. The depth h may have a maximum value equal to the
thickness of the P-cap layer 3, that is, 0 nm<h.ltoreq.H. That
is, in a thickness direction of the P-cap layer 3, the electric
field modulation region 5 necessarily extends from the surface of
the P-cap layer 3 close to the gate 23 to a side of the P-cap layer
3 distal to the gate 23, and the electric field modulation region 5
may extend into only a portion of the P-cap layer 3, as shown in
FIGS. 2 and 3, or may penetrate through the P-cap layer 3, as shown
in FIG. 4.
[0056] In an embodiment, of the two electric field modulation
regions 5, one close to the source 21 is a first electric field
modulation region 51, and the other close to the drain 22 is a
second electric field modulation region 52.
[0057] An edge of the first electric field modulation region 51
close to the source 21 is the edge of the P-cap layer 3 close to
the source 21, and an edge of the first electric field modulation
region 51 distal to the source 21 is between a first limit and a
second limit. The first limit is at a side of a first edge line
close to the source 21 with a distance of 400 nm from the first
edge line, the second limit is at a side of the first edge line
distal to the source 21 with a distance of 500 nm from the first
edge line, and the first edge line is an edge line, close to the
source 21, of a contacting area between the gate 23 and the P-cap
layer 3.
[0058] An edge of the second electric field modulation region 52
close to the drain 22 is the edge of the P-cap layer 3 close to the
drain 22, and an edge of the second electric field modulation
region 52 distal to the drain 22 is between a third limit and a
fourth limit. The third limit is at a side of a second edge line
close to the drain 22 with a distance of 400 nm from the second
edge line, the fourth limit is at a side of the second edge line
distal to the drain 22 with a distance of 500 nm from the second
edge line, and the second edge line is an edge line, close to the
drain 22, of the contacting area between the gate 23 and the P-cap
layer 3.
[0059] That is, the two electric field modulation regions 5 in the
P-cap layer 3 may be referred to as the first electric field
modulation region 51 and the second electric field modulation
region 52, respectively. Hereinafter, a preferred size range of the
electric field modulation region 5 is described by taking the first
electric field modulation region 51 close to the source 21 as an
example.
[0060] As shown in FIGS. 2 to 4, the edge of the first electric
field modulation region 51 close to the source 21 (i.e., the left
edge of the first electric field modulation region 51 in the
figure) is the edge of the P-cap layer 3 close to the source 21.
That is, the first electric field modulation region 51 may extend
to the edge of the P-cap layer 3 close to the source 21.
[0061] It can be seen that the gate 23 and the P-cap layer 3
necessarily have a contacting area, and position of an edge at the
side of the first electric field modulation region 51 distal to the
source 21 (i.e., the right edge of the first electric field
modulation region 51 in the figure) is defined as follows.
[0062] Here, an edge of the contacting area close to the source 21
(the left boundary of L1 in FIG. 3 or the right boundary of L2 in
FIG. 4) is the first edge line. As shown in FIG. 3, the edge of the
first electric field modulation region 51 distal to the source 21
(i.e., the right edge of the first electric field modulation region
51 in the figure) may be farther from the source 21 than the first
edge line (i.e., on the right side of the first edge line) by a
distance having a maximum value of 500 nm, i.e., L1 in FIG. 3 has a
maximum value of 500 nm. Alternatively, as shown in FIG. 4, the
edge of the first electric field modulation region 51 away from the
source 21 (i.e., the right edge of the first electric field
modulation region 51 in the figure) may be closer to the source 21
than the first edge line (i.e., on the left side of the first edge
line) by a distance having a maximum value of 400 nm, i.e., L2 in
FIG. 4 has a maximum value of 400 nm.
[0063] As such, the edge of the first electric field modulation
region 51 distal to the source 21 (the right edge of the first
electric field modulation region 51 in the figure) should be
between the two boundaries of L1 and L2 when L1=500 nm and L2=400
nm.
[0064] Needless to say, in a case where the edge of the first
electric field modulation region 51 distal to the source 21 is
farther from the source 21 than the edge of the contacting area
(i.e., the case shown in FIG. 3), the first electric field
modulation region 51 cannot contact with the second electric field
modulation region 52; in a case where the edge of the first
electric field modulation region 51 distal to the source 21 is
closer to the source 21 than the edge of the contacting area (i.e.,
the case shown in FIG. 4), the P-cap layer 3 necessarily has a
portion that is closer to the source 21 than the contacting area
but not the first electric field modulation region (i.e., the
portion left to the right boundary of L2 in FIG. 4), which will not
be described in detail herein.
[0065] Needless to say, it should be understood that the
limitations of preferred position and size of the second electric
field modulation region 52 in the P-cap layer 3 correspond to those
of the first electric field modulation region 51, and the only
difference therebetween is that the source 21 is replaced with the
drain 22, and therefore detailed description is omitted herein.
[0066] Needless to say, it should be understood that although the
preferred position and size range are the same, this does not mean
that in each transistor, the sizes of the first electric field
modulation region 51 and the second electric field modulation
region 52 are the same, i.e., forms of the two electric field
modulation regions are not required to be the same.
[0067] The P-cap layer 3 and the electric field modulation region 5
that meet the above size requirements can not only achieve the
basic functions of the transistor but also achieve a good effect of
reducing electric field at the edge of the Schottky junction, and
thus are preferable.
[0068] The embodiment also provides a method for manufacturing the
above transistor, which includes:
[0069] a step of forming the channel layer 11 and the barrier layer
12, a step of forming the P-cap layer 3 having the electric field
modulation region 5, and a step of forming the source 21, the drain
22, and the gate 23.
[0070] That is, the structures may be separately formed, so as to
obtain the transistor. Needless to say, it should be understood
that an order of forming the structures may be different depending
on form of the transistor and a specific manufacturing process, and
therefore, the literal order of the above steps does not limit the
order of forming the respective structures.
[0071] Specifically, the method for manufacturing the transistor
may include the following steps.
[0072] In S101, the substrate 9 is provided.
[0073] That is, the substrate 9 is provided as a base of other
structures of the transistor.
[0074] Specifically, the substrate 9 may be made of a material
selected from any one of silicon (Si), sapphire, aluminum nitride
(AlN), gallium nitride (GaN), silicon carbide (SiC), and the
like.
[0075] In S102, optionally, the transition layer 7 is formed.
[0076] In order to better match the material of the substrate 9
with materials of the channel layer 11 and the barrier layer 12, a
transition layer 7 for transition and buffer may be firstly formed
on the substrate 9, and the transition layer 7 may be formed by
epitaxial growth.
[0077] Specifically, the transition layer 7 may be made of a
material including any one or more of gallium nitride (GaN),
aluminum nitride (AlN), aluminum gallium nitride (AlGaN).
[0078] In S103, the channel layer 11 and the barrier layer 12 are
formed.
[0079] That is, the channel layer 11 and the barrier layer 12 are
formed sequentially.
[0080] The channel layer 11 is formed first, the barrier layer 12
is then formed, and subsequently, the P-cap layer 3 is formed.
[0081] In an embodiment, in this step, the channel layer 11 and the
barrier layer 12 are formed separately by epitaxial growth.
[0082] That is, the above channel layer 11 and barrier layer 12 may
be separately formed by an epitaxial growth process.
[0083] Specifically, the channel layer 11 may be made of a material
including any one of gallium nitride (GaN), aluminum gallium
nitride (AlGaN), indium gallium nitride (InGaN), aluminum indium
gallium nitride (AlInGaN) and indium aluminum nitride (AlInN); the
barrier layer 12 may be made of a material including any one or
more of gallium nitride (GaN), aluminum gallium nitride (AlGaN),
indium gallium nitride (InGaN), aluminum indium gallium nitride
(AlInGaN), and indium aluminum nitride (AlInN), and at least one
material in the barrier layer 12 have a band gap greater than a
band gap of the material of the channel layer 11.
[0084] In S104, optionally, as an implementation of the embodiment,
a P-type semiconductor material layer 39 is formed, and two regions
of the P-type semiconductor material layer 39 spaced apart from
each other are respectively doped to form high resistance zones 59
by ion implantation, and then the P-type semiconductor material
layer 39 is etched such that the remaining P-type semiconductor
material layer 39 forms the P-cap layer 3 and the remaining high
resistance zones 59 form the electric field modulation regions
5.
[0085] An "etching process" herein includes steps of forming a
material layer, coating a photoresist, exposing, developing,
etching, removing the photoresist, and the like, which will not be
described in detail herein.
[0086] That is, a complete P-type semiconductor material layer 39
may be formed first, obtaining the structure shown in FIG. 5. Then,
ion implantation is performed on at least regions corresponding to
the electric field modulation regions 5 in the layer so that the
implanted regions form high resistance zones 59, obtaining the
structure shown in FIG. 6. Finally, undesired portion of the P-type
semiconductor material layer 39 is etched off, and the remaining
portion naturally becomes the P-cap layer 3 having the electric
field modulation regions 5, obtaining the structure shown in FIG.
7.
[0087] According to the above method, as shown in FIG. 6, regions
to be removed in the P-type semiconductor material layer 39 may
also be ion-implanted because the P-type semiconductor material
layer 39 exists in these regions, thus the implanted ions will not
affect the barrier layer 12 and the like under the P-type
semiconductor material layer 39, and because the P-type
semiconductor material layer 39 in these regions is finally
removed, the structure of the transistor is not affected regardless
of whether or not the P-type semiconductor material layer 39 in
these regions is doped. Therefore, according to the above process,
even if there is a certain deviation in alignment during the ion
implantation, the barrier layer 12 and the like will not be
affected, and the process has high reliability.
[0088] Specifically, ions implanted in the ion implantation are
ions generally used for forming a high resistance zone in a P-type
semiconductor material layer, and may include any one or more of
argon (Ar), fluorine (F), nitrogen (N), oxygen (0), silicon (Si),
iron (Fe), carbon (C), boron (B), and the like.
[0089] Alternatively, as another implementation of the embodiment,
this step may also include: forming a P-cap layer 3, and doping two
side edge regions of the P-cap layer 3 respectively close to the
source 21 and the drain 22 by ion implantation to form high
resistance zones, and the high resistance zones being the electric
field modulation regions 5.
[0090] That is, the P-type semiconductor material layer 39 may be
etched first to form the P-cap layer 3, and then the corresponding
regions of the P-cap layer 3 may be ion-implanted to form the
electric field modulation regions 5.
[0091] In S105, the insulating layer 8, the source 21, the drain
22, and the gate 23 are formed.
[0092] That is, the insulating layer 8, the source 21, the drain
22, the gate 23, and other structures are formed according to
conventional processes to obtain the transistor shown in FIG. 2,
and the manufacturing is completed.
[0093] It could be understood that the above implementations are
merely exemplary implementations for illustrating the principle of
the present disclosure, but the present disclosure is not limited
thereto. For a person of ordinary skill in the art, various
variations and improvements may be made without departing from the
spirit and essence of the present disclosure, and these variations
and improvements are also considered to be within the protection
scope of the present disclosure.
* * * * *